Which of the following phenomena can be demonstrated by light,but not with sound waves in an air column?

The angle between the polarizer and the analyzer is $45^o$. The percentage of polarized light passing through the analyzer is........$\%$

Consider the following statements $A$ and $B$. Identify the correct choice in the given answers.
$A$. The refractive index of the extra-ordinary ray depends on the angle of incidence in double refraction.
$B$. The vibrations of light waves acquire one-sidedness for both ordinary and extraordinary rays in double refraction.

$A$ plane polarised light passes through successive polarisers which are rotated by $30^{\circ}$ with respect to each other in the clockwise direction. Neglecting absorption by the polarisers and given that the first polariser's axis is parallel to the plane of polarisation of the incident light,the intensity of light at the exit of the fifth polariser is closest to

An unpolarized beam of intensity $2a^2$ passes through a thin polaroid. Assuming zero absorption in the polaroid,the intensity of emergent plane-polarized light is

Plane polarised light is passed through a polaroid. On viewing through the polaroid,we find that when the polaroid is given one complete rotation about the direction of the light,one of the following is observed: